I was building a 24x16 shed and borrowed a Bostitch air frame gun from a friend and after six hours of working with it i found that it was doing a very good job driving nails,a heavy tool,but i expected that part.The next morning every bone and muscle from my hand to my shoulder hurt.I mentioned it to a contractor friend who lent me a Porter Cable air framer,FR350A,also heavy and it did a good job driving nails.I noticed that my arm to shoulder didn`t ache anywhere near the same as when i used the Bostitch.My friend,a contractor, told me the Porter Cable had much better balance and ergonomics than the Bostitch and that`s why he prefered the Porter Cable.I purchased the Porter Cable on Ebay and finished the shed.Another advantage the Porter Cable had was the fact you didn`t need to change triggers or have additional tools for adjustments,whereas the Bostitch took time to change triggers and tools for adjustments.I also added heavy wooden shelving in the shed and also in my garage.This nail framer performed flawlessly and i learned that the Porter Cable was a well thought out ergonomically correct tool compared to the Bostitch.I am half way finished putting an addition to my deck and again the Porter Cable has proven that ergonomics and performance are vital in the comfort of no aches or pains to do a job.I have lent this air framer to my neighbor who is also building a work shed and he commented that he was surprised by the performance and balance of this make and model.I am retired and i own numerous tools from several manufacturers,but my body told me that there is a big difference in the use of a heavy air nail framer by manufacturer. I highly reccommend the Porter Cable framer to anyone who is thinking of buying a air nail framer gun.           H.RICHMAN,MARYLAND